如何从Model触发PropertyChanged通知以刷新View？

我在更新列表中对象的属性值时，View无法自动刷新；但给列表添加新项时，View能正常刷新。

已实现的基类ViewModel（INotifyPropertyChanged） #

public class BaseViewModel : INotifyPropertyChanged
{    
    protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
    {
        var changed = PropertyChanged;
        if (changed == null)
            return;

        changed.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }
    #endregion
}

业务ViewModel代码 #

public class SAVSplitViewModel : BaseViewModel
{
    public ObservableCollection<ListItem> Items
    {
        get { return primaryBin.Items; }
        set { primaryBin.Items = value; OnPropertyChanged(); }
    }

    public ObservableCollection<ListItem> CurrentItems
    {
        get 
        {
            if (IsPrimaryBin)
                return primaryBin.Items;
            else
                return secondaryBin.Items;
        }
        set
        {
            if (IsPrimaryBin)
                primaryBin.Items = value;
            else
                secondaryBin.Items = value;
        }
    }

    public ObservableCollection<ListItem> NotCurrentItems
    {
        get
        {
            if (!IsPrimaryBin)
                return primaryBin.Items;
            else
                return secondaryBin.Items;
        }
        set
        {
            if (!IsPrimaryBin)
                primaryBin.Items = value;
            else
                secondaryBin.Items = value;
        }
    }
}

触发属性更新的业务代码 #

if (Found) 
{
    viewModel.IsBusy = true;

    //检查是否已收到该产品
    ListItem origin = viewModel.CurrentItems.FirstOrDefault(i => i.EAN == labelText);

    updateErp = false;
    SupplierOrderLineForScan p = viewModel.lines.FirstOrDefault(pr => pr.Ean.Trim() == labelText.Trim());
    u = await Common.GetPickingUser();

    //检查手推车上是否已有该产品
    ListItem bincontentDirection = viewModel.NotCurrentItems.FirstOrDefault(i => i.EAN == labelText);
    BinContent bincontentOrigin = viewModel.NotCurrentBinContents.Find(s => s.StockId == p.StockId);


    if (bincontentDirection == default(ListItem))
    {
        bincontentDirection = new ListItem { 
            Quantity = 0
            , EAN = origin.EAN, Name = origin.Name};
        viewModel.ItemsTransfer.Add(bincontentDirection);
    }
    bincontentDirection.Quantity++;
    origin.Quantity--;

}

尝试修改Model类（无效） #

public class BaseModel : INotifyPropertyChanged
{
    protected bool SetProperty<T>(ref T backingStore, T value,
        [CallerMemberName] string propertyName = "",
        Action onChanged = null)
    {
        if (EqualityComparer<T>.Default.Equals(backingStore, value))
            return false;

        backingStore = value;
        onChanged?.Invoke();
        OnPropertyChanged(propertyName);
        return true;
    }

    #region INotifyPropertyChanged
    public event PropertyChangedEventHandler PropertyChanged;
    protected void OnPropertyChanged([CallerMemberName] string propertyName = "")
    {
        var changed = PropertyChanged;
        if (changed == null)
            return;

        changed.Invoke(this, new PropertyChangedEventArgs(propertyName));
    }

}

public class ListItem : BaseModel
{
    private int _quantity;
    public int Quantity
    {
        get { return _quantity; }
        set { SetProperty(ref _quantity, value); }
    }
}

问题原因及解决办法 #

1. 核心问题：primaryBin.Items和secondaryBin.Items的类型必须是ObservableCollection<ListItem>，而非普通List<ListItem>。只有ObservableCollection会将集合内对象的PropertyChanged事件传递给绑定系统，普通List做不到这一点。

2. 关键检查点：

   • 确认primaryBin和secondaryBin中的Items属性是ObservableCollection<ListItem>类型，比如：

     public class Bin
     {
         public ObservableCollection<ListItem> Items { get; set; } = new ObservableCollection<ListItem>();
     }
     

   • 调试确认修改Quantity时，ListItem的SetProperty方法确实触发了OnPropertyChanged，且PropertyChanged事件有订阅者（View的绑定已注册该事件）。
   • 检查View的绑定路径是否正确，确保绑定的是ListItem.Quantity属性。

3. 额外注意：你的CurrentItems和NotCurrentItems的getter直接返回primaryBin或secondaryBin的Items实例，这部分逻辑没问题，但前提是这些实例本身是ObservableCollection。

内容的提问来源于stack exchange，提问作者Elgate